High fashion trend and consumer needs in recent years have extremely been diversified, and in order to provide woven or knitted fabrics for clothes for demands of consumers, more improved touch and specialized function are needed. It has been desired to provide woven or knitted fabrics for clothes having such specialized functions that allow reversible variation of air permeability of clothes, and adjustment of temperature and humidity in clothes, depending on variation of temperature, humidity etc. in clothes, and thereby enabling consistent maintenance of environment in clothes in a comfortable state.
It has been conventionally known that natural fibers, such as cotton and wool, have reversibly changeable physical properties depending on moisture or water content. This high-level water retention of raw materials give slower speed in variation between a dried state and a wet state, resulting in slower air permeability variation and small difference of air permeability in the clothing.
For this reason, various investigations in synthetic fibers have been performed. For example, Patent Document 1 describes an air permeability self-adapting woven or knitted fabric comprising a compounded fiber having reversibly changeable percentage crimp based on humidity variation, the fiber being made of a modified polyethylene terephthalate containing sulfonate groups, and a nylon compounded in a state side by side.
However, both of the polyester and nylon in this method can only demonstrate insufficient water absorption property and moisture absorption property, and can provide small variation of form owing to humidity or water content, leading to insufficient air permeability variation, and unsatisfactory water absorption property and quick-drying capability of woven or knitted fabrics obtained.
In addition, Patent Document 2 describes a woven or knitted fabric using a cellulose acetate fiber obtained by alkali treatment of a fiber through compound spinning, into a shape side by side at a predetermined weight ratio, of cellulose acetates exhibiting reversibly crimping performance and having difference of average degree of substitution not less than a predetermined value. The fabric cannot demonstrate neither sufficient dimensional stability as a woven or knitted fabric, nor quick-drying capability because of reversible change of crimp by means of humidity.
Patent document 1: Japanese Patent Application Laid-Open Publication No. 2003-41462
Patent document 2: Japanese Patent Application Laid-Open publication No. 2002-180323